1. Field of the Invention
The present invention relates to a high protein, extrusion processed, texturized sinking food for marine life (e.g., shrimp and fish) which contains a substantial quantity of marine meal. The starting material is first preconditioned and then extruded to yield a shrimp and fish food preferably having a specific gravity greater than 1.0 which is self-sustaining in water for a period of at least four hours. The particular specific gravity desired may be controlled by process conditions. The resulting product contains a high content of fish oil, an essential nutrient for fish, shrimp and other marine life. The food hereof is in the form of a texturized product having a plurality of gas cells therein, whereby feeding shrimp or fish may eat the outer portion without causing product breakup an unacceptably high dissipation of nutrients into the surrounding water.
2. Description of the Prior Art
An increasing demand for high quality protein sources has resulted in the flourishing aquaculture industry, whereby fish, shrimp and other marine life are raised commercially much in the manner of cattle, hog and other livestock. As the aquaculture industry has developed, a demand has arisen for a high quality, nutritional sinking food which will produce optimum yields from the marine life being cultured.
It has been determined that a sinking food is most desirable in raising cultured marine life, inasmuch as it most closely accommodates their natural feeding tendency to bottom feed. In the past, two principal methods have been employed in attempting to make a satisfactory sinking fish food. Uncooked, pelletized products have been produced using conventional pellet mills. Such products typically include high proportions of marine (fish) meal, a prime nutrient in these feeds. However, such pelletized feeds suffer from the fact that they do not satisfactorily retain their structural integrity in the water, resulting in rather rapid dissipation in water. High nutrient dissipation lessens the food value of the product and can pollute the water in which the fish or shrimp are raised. In addition, such pelletized products require the addition of a binder, providing little additional nutrition to the fish but requiring an added expense.
On the other hand, past extruded fish foods of farinaceous composition have been essentially amorphous products which tend to "puff up" in water and become mushy. As a result, these products also tend to dissipate nutrients into the surrounding water, particularly when a shrimp bites into the feed.
In order to be truly acceptable, a sinking marine food should be essentially self-sustaining in water for a period of at least about 4 hours. This would permit the aquaculturist to periodically introduce the feed into water at convenient times, without fear of undue nutrient dissipation or product breakup. At the same time however, such a marine food should contain proper nutrients such as relatively high contents of marine meal and oils.